Cell reselection is one of the most basic processes of a cellular mobile communications system. A mobile phone needs to perform cell reselection constantly while moving, so as to ensure quality of service. In the process of cell reselection, timely selection of a suitable target cell directly determines network camping performance of the mobile phone.
For a specific standard (for example, GSM), a typical cell reselection process is as follows: In order to avoid frequent ping-pong reselection, a criterion for cell reselection is to control a cell reselection behavior of a terminal by using two parameters: a hysteresis signal strength (which is usually 3 dBmV dBm) and a hysteresis time (which is usually set to 5 s). When a strength (for example, −72 dBm) of a signal received from a target cell is greater than a signal strength (−80 dBm) of a serving cell plus the hysteresis signal strength (3 dBm) and duration is greater than the hysteresis time (for example, 5 s), cell reselection is started; otherwise, the terminal continues to camp on the current serving cell.
In a scenario of high-speed movement (for example, in a network covering a high-speed train), when a user takes a fast-running automobile or train (especially a high-speed train), because a terminal moves excessively fast, cell signals may change quickly, where usually, a signal of a serving cell weakens quickly while a signal of a target cell strengthens quickly, which leads to frequent occurrences of a case like this: in a process of determining a to-be-reselected cell, a terminal already leaves a coverage area of a current serving cell before duration reaches a hysteresis time, but the determining of a to-be-reselected cell is not completed yet; and after the serving cell is unable to provide a service, the terminal has still not accessed a target cell whose signal is relatively great, and accesses the target cell only after temporary disconnection from a network, where the temporary disconnection from the network makes a user unable to enjoy a communication service or makes an ongoing communication service interrupted, which directly causes deterioration of user experience.